1. Field of the Invention
The present invention relates to improvement of an optical electronic apparatus equipped with an image blur prevention function suitable for a camera, a digital camera and the like.
2. Related Background Art
In recent years, a zooming function is generally used in optical electronic apparatuses such as a silver salt camera, a digital camera and a video camera. In particular, an apparatus capable of performing high-magnification photographing (image recording) has become the mainstream.
In addition, an optical electronic apparatus with an image blur prevention function is generally used in order to solve a problem that image quality is significantly affected by a subtle movement (hand vibration) of a photographer as magnification is made higher.
As this image blur prevention function, there are various systems such as an electronic system mainly adopted in a video camera and the like and an optical system mainly adopted in a silver salt camera, a digital camera and the like.
Among the various systems of the image blur prevention function, a most generally used optical image blur prevention function is for driving a blur correction optical system (hereinafter referred to as shift lens), which is an element of an image blur prevention system included in a part of a photographing optical system, based on an output of vibration detecting means (vibration gyro, etc.) installed in a housing of an optical electronic apparatus such as a camera to reduce image blur on an image pickup surface of a film (or CCD, etc.) during an exposure operation (or image recording operation), that is, while a shutter is driven (open).
A system is often used which performs control of the above-mentioned shift lens by a permanent magnet adhered to the shift lens and a coil (electromagnet) of a camera main body or the like, which is installed in a position opposite the permanent magnet, to adjust a magnetic force to be generated and control an amount of movement of the shift lens according to an amount of energization to the coil.
It is preferable to drive the shift lens by controlling an electric current to the coil. However, since the amount of movement of the shift lens should be changed according to an amount of vibration, xe2x80x9cPulse Width Modulation (hereinafter referred to as PWM) controlxe2x80x9d in accordance with a voltage is often performed in order to actually drive the shift lens with good follow-up ability. Voltage detecting means for judging whether or not a voltage capable of driving an electronic apparatus is present is driven in advance, and a reference of PWM control that is a drive pattern of the shift lens is generally determined based on a result of voltage detection.
Moreover, methods of controlling an optical image blur prevention function are roughly divided into a method of performing xe2x80x9cfeedback controlxe2x80x9d that realizes an image blur prevention effect by recognizing an absolute position of the shift lens and moves the shift lens to a position according to an amount of vibration and a method of xe2x80x9copen controlxe2x80x9d that always performs control of the shift lens according to an amount of vibration as driving from an initial position without a position detecting mechanism of the shift lens itself.
Since the above-mentioned xe2x80x9cfeedback controlxe2x80x9d can recognize an absolute position of the shift lens, it becomes possible to judge whether or not the image blur prevention effect is realized or to detect a failure of the image blur prevention system (disconnection, etc.). Thus, a degree of completion of the system is high. However, on the other hand, a sensor for detecting a shift lens position (PSD, etc.) is required. Therefore, the xe2x80x9copen controlxe2x80x9d system is more advantageous in terms of space and costs.
There is a tendency of xe2x80x9cminiaturizingxe2x80x9d an apparatus which attaches importance to portability as another stream in the optical electronic apparatus market. Thus, a power supply such as a battery used in the apparatus tends to be also miniaturized and made smaller in capacity. As a result, energy saving of the entire apparatus has to be realized. Therefore, in order to prevent energy from being used more than needed, control for switching an energization current during driving is performed for an actuator that consumes a relatively large amount of energy.
More specifically, for example, as shown in FIG. 9, a large amount of energization current (consuming energy) is required (I1) in time (t1) from a closed state to a fully opened stable state for driving of a shutter (shutter also functioning as a stop) of a compact camera or the like. However, holding of the fully opened state (T-t1) and a closing operation from the fully opened state (t2) can be executed with a small amount of energization current (I2, I3). Thus, consuming energy (energization current) of the actuator (shutter) during exposure operation is often varied.
In addition, from a viewpoint of xe2x80x9cminiaturizationxe2x80x9d, if the image blur prevention function is provided, xe2x80x9copen controlxe2x80x9d is often used as control of the image blur prevention system. Conventionally, since a drive pattern (e.g., PWM reference voltage) of the image blur prevention system (shift lens, etc.) is determined to be one in advance, if consuming energy of the actuator varies during driving of the image blur prevention system, energy (voltage) that can be used for the image blur prevention system varies. Thus, there is possibility that the image blur prevention system cannot operate with a desired amount of driving and an image blur prevention effect is reduced despite the fact that the image blur prevention system is driven with a planned drive pattern.
A specific example is shown in FIG. 10.
Given that an optical electronic apparatus vibrated at a predetermined frequency is subject to the PWM control for a shift lens so as to correct the vibration, as long as a proper drive pattern (driving signalxe2x80x94amount of shift lens movement) of the shift lens is set at a voltage V1 before consuming energy of an actuator varies, shift lens driving with proper vibration suppression can be performed until consuming energy of the actuator is varied.
However, if consuming energy of the actuator is varied (reduced) and the shift lens is controlled with the same drive pattern as that at time V1 at a stage where a voltage that can be used for driving shift lens reaches V2, an actual correction amount (shift lens driving amount) becomes larger than a proper correction amount. Thus, a control error (correction error) occurs, and a situation arises in which an image blur prevention effect is reduced despite the fact that the image blur prevention system is actuated.
If control of the image blur prevention system is the xe2x80x9cfeedback controlxe2x80x9d system, it is possible to recognize reduction of the image blur prevention effect to perform self correction. However, in the xe2x80x9copen controlxe2x80x9d system, it is difficult to perform the self correction.
As a measure for dealing with the above-mentioned problem, Japanese Patent Application Laid-Open No. 7-295001 proposes to repeat a voltage detecting operation even during an exposure operation to perform shift lens driving based on a result of the detecting operation.
However, it takes time for calculation as a sequence to repeat voltage detection during an exposure operation as in the above-mentioned proposal. Thus, it is likely that temporal delay occurs from the time of hand vibration until the shift lens is driven, and controllability and effects as an image blur prevention system are reduced by half.
The present invention has been devised in view of the above and other drawbacks, and therefore it is an object of the present invention to provide an optical electronic apparatus equipped with an image blur prevention function with which a desired image blur prevention effect can be realized even if an energy saving operation required for miniaturizing the apparatus is performed.
According to the present invention, there is provided an apparatus or a camera provided with an image blur prevention function, characterized by comprising: a blur correction driving means for performing correction of image blur; an actuator separate from the blur correction driving means, consuming energy of the actuator changing depending on time; a power supply for supplying energy to the blur correction driving means and the actuator; and a variable circuit for changing an energy supply pattern in supplying energy to the blur correction driving means by the power supply before or after consuming energy of the actuator changes.
Particularly, in the apparatus, the blur correction driving means is controlled to be driven by pulse width modulation control and the variable circuit changes a pulse width.
Also, in the apparatus, the actuator is controlled by variation in current of the power supply.
Further, the apparatus includes: an image receiving medium for receiving a subject image; and a shutter member for changing an amount of light reaching the image receiving medium, and in the apparatus, the actuator corresponds to the shutter member.
Further the apparatus includes optical means for forming an optical image of a subject, and in the apparatus the blur correction driving means drives at least a part of optical units constituting the optical means.
Further, the apparatus includes a voltage detection circuit for detecting a voltage of the power supply, and in the apparatus the voltage detection circuit detects a voltage in a state in which energy is supplied to the actuator.
Further characteristics of the present invention will be apparent from the following description and the drawings.